Questions You Should Know about Arsenic Reduction Furnace

WATKINS [Advanced Refining Technologies (ART)]

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Arsenic is a significant concern due to its nature as a persistent poison. Typically, we observe about 60° Floss per weight percent pickup, which necessitates attention. Note that arsenic is prevalent in most fractions during hydrotreating processes, ranging from naphtha to heavy gas oil. Various process variables, catalysts, and operating conditions will define the point at which a dedicated trap is necessary. This primarily depends on how much arsenic enters your reactor and the other catalysts involved. Monitoring the daily arsenic intake in your hydrotreater is crucial for evaluating deactivation control mechanisms.

Factors Influencing Arsenic Pickup

The chart on the slide highlights the correlation between arsenic pickup on the catalyst and the actual nickel concentration in the reactor. A significant determinant for arsenic retention in your reactor is the amount of nickel present. As you progress from lower to higher nickel concentrations, arsenic pickup can dramatically increase.

Operating temperature also plays a crucial role in arsenic retention. Monitoring the weighted average bed temperature or the actual catalyst temperature is essential. For example, a diolefin reactor operating at 250°F to 300°F results in minimal arsenic pickup, while temperatures ranging from 650°F to 700°F can significantly increase arsenic absorption depending on catalyst placement. These factors will ultimately guide the volume needed for guard catalysts in your reactor.

Phosphorus Pickup

Phosphorus presents similar challenges; around 1 wt% pickup leads to approximately a 10°F loss in activity. This degradation worsens with higher phosphorus levels on the catalyst. The spent catalyst analysis table provided shows phosphorus accumulation even in guard materials, indicating temperature dependency. The focus should be on catalyst quantity in your hydrotreater, as it determines the necessity for trap material. We recommend conducting spent catalyst analysis for further insights.

SIVADASAN (UOP LLC, A Honeywell Company)

Arsenic is particularly harmful to hydroprocessing catalysts, with its impact closely linked to crude sources. The catalytic reactions dictate arsenic's effect, as seen in the ULSD units where indirect hydrogenation prefers low arsenic concentrations, affecting catalyst performance significantly. Conversely, in 500 ppm diesel processing, catalysts can tolerate up to 1 wt% arsenic before a notable reduction in lifespan occurs. Given the variability in arsenic concentrations, cycle lengths, and electro conditions, establishing a fixed threshold concentration for dedicated arsenic traps remains challenging.

Phosphorus can enter the system from various routes, including crudes and other biofeeds. Its effect is comparable to sodium levels, as 1 wt% sodium can reduce catalyst activity by over 50%. The performance fluctuates based on the phosphorus source and form.

Best Practices for Arsenic and Phosphorus Analysis

MUKESH PATEL (Reliance Industries Ltd.)

Determining arsenic levels can be challenging due to lab analysis interferences. Generally, a cycle followed by a spent catalyst analysis allows estimation by back-calculating feed arsenic levels.

WATKINS [Advanced Refining Technologies (ART)]

The optimal amount of trap is dependent on both main bed and guard catalysts. Utilizing a high-nickel catalyst can balance activity to prolong cycles. Factors influencing cycle length and arsenic absorption ultimately hinge on temperature and daily intake rates. Consulting your catalyst supplier to establish an effective system is advisable.

Impact of Arsenic on Catalyst Activity

Arsenic (As) is prevalent in various crude oils, particularly those from West Africa and Russia. Its increasing presence poses risks as synthetic crude usage rises. Arsenic binds with metal sulfide sites, significantly impacting catalyst productivity. Research by ART shows that 1,000 ppm of arsenic corresponds to a 5°F loss in hydrodesulfurization (HDS) activity. As arsenic concentration increases to 1 wt%, the activity loss surges beyond 50°F.

Temperature also plays a critical role in arsenic absorption rates, as shown in various catalysts. For instance, figures indicate that high-nickel catalysts effectively trap arsenic; however, environmental conditions significantly influence the ultimate arsenic retention capabilities.

Phosphorus Contamination

Phosphorus contamination primarily stems from fracturing fluids in crude oils, especially from the Western Canadian Sedimentary Basin. Its presence leads to catalyst deactivation. A 1 wt% phosphorus level results in about a 10°F reduction in catalyst activity. Maintaining feed levels below 0.5 wppm, alongside feed filtration, is advisable to mitigate phosphorus sediment.

ART's studies have indicated that high levels of various poisons, including arsenic and phosphorus in hydrotreaters, lead to rapid catalyst degradation. This highlights the necessity for precise monitoring and effective protective measures.

RAJESH SIVADASAN (UOP LLC, A Honeywell Company)

For further information on the Arsenic Reduction Furnace, please contact us for an expert consultation!